The present invention relates to an apparatus for heating and/or drying of wet, comminuted material such as, for example, organic material.
A heating and/or drying apparatus of the aforementioned type generally include a rotatable hollow rotor with an inlet and discharge reheat medium and possible condensate, with the rotor having annular polygonal drying elements disposed at intervals and hollow channels for the heat medium disposed in an annular manner.
Apparatus of the aforementioned type have been employed for the treatment of wet materials such as fishmeal, comminuted offal, mash from breweries and similar moist, glutinous materials of animal or vegetable origin and are usually designed for high performance such as, for example, the drying of several tons of material at a time.
In, for example, Danish Patent No. 138,406, an apparatus of the aforementioned type is proposed wherein the annular channels with hollow spaces for the heating medium in each drying element are in the form of a spiral for the through-flow of steam. The channels are spiral shaped so as to more easily drive the condensate out of the channels thereby achieving a good and continuous through-flow of steam.
A disadvantage of the utilization of spiral-shaped channels resides in the fact that the production costs and procedures are considerable since, in practice, the spiral shape is produced by a composition of circular sectors of suitably curved bands of plate material, with the plate material being welded onto the disk-shaped rotors through difficult welding processes. Moreover, the ends of the curved bands must also be welded together, pressure tight and generally executed in stainless materials.
The aim underlying the present invention essentially resides in providing an apparatus of the aforementioned type which is constructed in such a manner that production, to a great extent, is facilitated without giving rise to other disadvantages.
In accordance with advantageous feature of the present invention, an apparatus for heating and/or drying of wet comminuted material is provided having at least two annular channels to which the heating medium is fed in parallel, with annular drying elements being provided each of which comprise two plates coupled together to one drying element. At least one of the plates is deformed in such a manner that the channels are formed and the two plates are joined directly together by welding.
The object of the invention is to provide an apparatus of the kind in question, but of such a configuration that the production is to a great extent made easier without hereby giving rise to other disadvantages.
By virtue of the above noted features of the present invention, it is possible to feed several channels in parallel at one time, which gives a more uniform distribution of heat in the drying element and the possibility for the supply of more thermal energy than with the known constructions. In practice, no problems arise with possible condensate if the heating is effected by steam. The heating can, however, also be carried out with, for example hot oil or the like. The supply of large amounts of thermal energy is of great importance if, for example, the comminuted material shall be boiled and possibly sterilized as quickly as possible.
With the new configuration of the apparatus, positioning of the annular channels, since the annular channels be placed in any position over the whole of the drying elements, i.e. in a one-sided or two-sided formation and closely at the side of each other, or with a distance between them. In accordance with still further features of the present invention, the annular channels are configuration on both sides of the drying elements so that a very great supply of thermal energy can be achieved together with a uniform heating of the whole of the drying element.
The plates may, in accordance with the present invention, be roundels, with both roundels in each drying element being deformed for the formation of the channels. With such an arrangement, the production is simplified since the welding of the channel parts is avoided and the drying elements are produced by providing a plate with suitable deformation so that the desired channel pattern arises.
While the plates are preferably roundels, and it can be sufficient for one roundel in each pair to be deformed for the formation of channels, however, according to the invention, the two annular channels do not necessarily have the same cross-sectional area, whereby the possibility is provided for channels of greater cross-sectional area and thus a greater supply of thermal energy, hereby increasing the capacity of the apparatus. This channel configuration also offers advantages from the point of view of production technology.
Since the annular channels in each drying element are not, in fact, of equal length, they do not have the same resistance to flow. In order to achieve a uniform temperature distribution across each drying element, the channels may have a greater cross-sectional area the greater the distance from the channels and/or the annular channels may be disposed in a circular manner on the drying element.
In accordance with yet further features of the present invention, the circular channels are advantageously concentric with respect to each other, whereby, the whole of the welding operation involved in welding the channels onto the drying elements can be automated and carried out by simple welding robots, and a very even and uniform weld seam requiring the minimum of aftertreatment is achieved.
The circular channels may also, in accordance with the present invention be concentric with the drying element and the rotor and/or an outer edge of the annular drying elements may be of a polygonal configuration, whereby, the possibility is provided for a large number of channels on each drying element, and herewith a great supply of thermal energy.
According to the present invention, the annular channels may be of a polygonal configuration corresponding to the outer edge of the annular drying element and/or the outer edge of the drying element may be a quadratic, whereby changes can be made in the pattern of the stirring and the heat distribution, e.g. depending on what kind of materials are to be handled. In accordance with additional features of the present invention, a supply channel for the heating medium may be disposed on one side of the heating element with a return channel for the heating medium being disposed on the other side of the drying element. By virtue of this arrangement, an optimum utilization of raw materials is realized in that the drying elements can be produced by the shearing of lengths of material which are then worked up in the formation of channels, etc. with the heating medium supplied on the one side of the drying element and the return flow on the other side according to the present invention the channels can be executed in an almost completely annular manner. Thereby resulting in a very uniform heat distribution, and it is avoided that the supply channel and the return channel lie in each other's way during the welding operation. With some embodiments of the drying element, it can be advantageous that both the supply channel and the return channel are positioned on the same side, for example on the same side as the channels.